Regarding characteristics of radio transmission that utilizes spatial propagation, transmission performance may vary due to environmental conditions about weather, obstruction, or the like. Therefore, when the weather condition is bad, the radio transmission should be operated within a restricted frequency band.
On the other hand, since optical transmission utilizes an optical fiber as a transmission medium, it has a risk such that the optical fiber may be broken off due to an earthquake, a fire, road work, or the like. Therefore, if an optical fiber for optical transmission is broken off due to an earthquake or the like, a detour should be established so as not to use the broken line, and the broken optical fiber should be restored.
A technique relating to the present invention is shown in Patent-Document 1.